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In the shade

By Alison Motluk

SHADOWS are helping to throw light on the writings of ancient Romans.

A cache of Roman tablets was discovered near Hadrian’s Wall in the mid-1970s,
but they are proving extremely difficult to read. The pine tablets, which are 5
centimetres by 10 centimetres, once held writings etched into a thin layer of
beeswax on their surface with a metal stylus. The tablets have spent the last
two thousand years lying in a pit and now all that remains of the writings are
faint scratches on grainy, badly-stained wood.

Now Alan Bowman, head of the Centre for the Study of Ancient Documents at the
University of Oxford, has teamed up with Mike Brady, an engineer also at Oxford,
to work on ways to read the writing. Brady developed a technique called “shadow
stereo” to measure the depth of the blind spot at the back of the eye. This is
now being refined for use on the tablets.

One of the big problems for classicists is separating script from stain.
Shadow stereo tracks how shadows change as a light source is moved around.
Knowing the angle and the height of the light source, researchers can calculate
where genuine shadows should fall and so identify the markings. “The shadow
boundaries of incisions will move in predictable ways,” says Brady. “The stains
won’t move.” He says the tricky part was making a filter that can pick out
subtle shades of grey.

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So far the technique has been used on 12 tablets, and the team hopes to do a
full trial on a wide variety next year. “We’d like to push towards harder cases
that they cannot read at all,” says Brady. Sometimes a tablet was reused, for
instance, and bears more than one set of scratches.

Brady says the team is considering developing a version to use in the field
on carvings.